The present invention relates to a technique for suppressing a howling.
Various techniques for suppressing a howling caused in an acoustic system including a sound collection device and a sound emission device have been proposed conventionally. For example, a howling suppression apparatus comprising an adaptive filter for generating a signal (hereinafter called an “estimated signal”) in which acoustics (hereinafter called a “feedback sound”) reaching a sound collection device from a sound emission device are estimated and a calculator for subtracting the estimated signal from an acoustic signal generated by the sound collection device in a time domain is disclosed in JP-A-2006-217542.
However, in the technique of JP-A-2006-217542, there are cases where a component which causes a howling cannot be eliminated from an acoustic signal completely. For example, when the acoustic signal differs from an estimated signal in a phase, a component (component which causes the howling) of a feedback sound remains in the acoustic signal after calculation by a calculator and the component circulates through an acoustic system and thereby, the howling increases cumulatively.